Surgical drill guides and systems

ABSTRACT

Surgical drill guides having a guide shaft and a set of distal guide teeth extending from the guide shaft. The guide shaft has proximal and distal portions having two distinct inner and outer diameters, with a tapered zone extending between the two portions. Wall thickness is maintained or increased from the proximal portion to the distal portion of the shaft, reinforcing the rigidity of both the shaft and the distal guide teeth.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 16/617,210, which in turn is the U.S. national phase entry under 35U.S.C. §371 of International Application No. PCT/US2018/039009, filedJun. 22, 2018, entitled SURGICAL DRILL GUIDES AND SYSTEMS, which in turnclaims priority to and benefit of U.S. Provisional Application No.62/523,451, filed Jun. 22, 2017, the contents of which are incorporatedherein by reference in their entirety for all purposes.

FIELD

This disclosure relates to surgical drill guides and, more particularly,to flexible drill guide systems for soft tissue repair.

BACKGROUND

Arthroscopic procedures using sutures and suture anchors have been usedin surgical repairs to, for example, secure soft tissue to bone. Asuture anchor delivery system is generally composed of an inserterdevice with an attached anchor, a drill for bone tunnel preparation, anda guide for introducing the drill into the repair site. The inserter andthe soft tissue anchor can also be introduced into the repair locationby means of the drill guide.

In current drill guide design, there are a number of competing featuresthat are important for establishing the position and trajectory of thepassing instruments to the repair site. For example, some repairsrequire anchors to be placed as close to an anatomic margin as possible.In these cases, guides having smaller distal outer diameters aredesirable, since this allows the center point of the guide shaft to becloser to the anatomical margin. However, narrowing the diameter at thedistal end of the guide generally results in sacrificing wall thicknessand rigidity of the distal teeth which allow for secure placement of theguide onto the bone. In curved guides, moreover, a larger inner diameteris desirable in the bent region to allow more room for the rigidportions of the passing instruments to navigate through. However, it isalso desirable for the inner diameter at the distal end of the guide tobe smaller in order to tightly constrain the exit trajectory of thepassing instruments, reducing the risk of iatrogenic damage. Somecurrent guides accommodate a smaller inner diameter at the distal end byhaving a larger radius of curvature and a smaller angle in the bent areaof the guide. However, this configuration is less desirable foraccessing hard-to-reach or hard-to-visualize anatomical areas.

BRIEF SUMMARY

Described herein is a surgical drill guide having a guide shaft and aset of distal guide teeth extending from the guide shaft. The guideshaft has proximal and distal portions having two distinct inner andouter diameters, with a tapered zone extending between the two portions.In the drill guide of this disclosure, wall thickness is maintained orincreased from the proximal portion to the distal portion of the shaft,reinforcing the rigidity of both the shaft and the distal guide teeth. Asmaller inner diameter in the distal portion of the shaft facilitates apredictable and accurate exit trajectory of passing instruments,allowing for a more anatomically accurate repair. Moreover, in curvedguides, a larger inner diameter is also maintained in the bent region ofthe curve, allowing for a smaller and more distal (relative to thehandle) bend radius and a larger bend angle of the guide, which isfavorable for accessing constricted areas.

Further examples of the surgical drill guide of this disclosure mayinclude one or more of the following, in any suitable combination.

In examples, the surgical drill guide of this disclosures includes ashaft having a proximal portion and a distal portion. The distal portionincludes a tapered portion and a distal end. An outer diameter of theproximal portion is selected to be larger than an outer diameter of thedistal end. The proximal portion and the distal end separated by thetapered portion. The guide also includes a bore defined by a wall of theshaft extending from a proximal end to the distal end of the shaft. Thewall defining a plurality of teeth extending from the distal end. Athickness of the wall of the distal end is selected to be the same as orgreater than a thickness of the wall of the proximal portion.

In further examples, the guide includes a handle coupled to the proximalend of the shaft. The shaft is made of a metal material. The distalportion of the shaft is angled relative to a longitudinal axis of theproximal portion. In examples of the angled shaft, the wall defines aflat section at a highest point of a bend in the distal portion and/orat least one of the plurality of teeth is modified or removed tofacilitate passage of the guide through a cannula. The distal portionincludes at least one transverse hole in communication with the bore. Inexamples, the tapered portion is formed in one piece or in multiplepieces. A projected plane across points of the plurality of teeth isangled with respect to an outer diameter of the distal end of the guide.An inner diameter of the distal portion is selected to be smaller thanan inner diameter of the proximal portion.

Examples of a surgical drill guide system of this disclosure include adrill guide having a shaft with a proximal portion and a distal portion.The distal portion includes a tapered portion and a distal end. An outerdiameter of the proximal portion is selected to be larger than an outerdiameter of the distal end. The proximal portion and the distal end areseparated by the tapered portion. The guide also includes a bore definedby a wall of the shaft extending from a proximal end to the distal endof the shaft, the wall defining a plurality of teeth extending from thedistal end. A thickness of the wall of the distal end is selected to bethe same as or greater than a thickness of the wall of the proximalportion. The system also includes a flexible drill extending through thebore from the proximal end to the distal end of the shaft.

In further examples, the drill is made of Nitinol. An As temperature ofthe Nitinol is selected to be greater than an operating temperature ofthe drill. At least a portion of the Nitinol is in a martensitic stateand the Nitinol is machined while in a superelastic state. The drillfurther includes a sheath which extends through the bore from theproximal end to a region proximal to the distal portion of the shaft.The sheath is made of a material selected to be more rigid than amaterial of the drill. The shaft is made of a metal material. The distalportion of the shaft is angled relative to a longitudinal axis of theproximal portion of the shaft. The distal portion includes at least onetransverse hole in communication with the bore. In examples, the taperedportion is formed in one piece or in multiple pieces.

These and other features and advantages will be apparent from a readingof the following detailed description and a review of the associateddrawings. It is to be understood that both the foregoing generaldescription and the following detailed description are explanatory onlyand are not restrictive of aspects as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be more fully understood by reference to thedetailed description, in conjunction with the following figures,wherein:

FIGS. 1-3 illustrate a prior art curved surgical drill guide;

FIGS. 4A-F illustrate an example of a surgical drill guide of thisdisclosure;

FIG. 5-6B illustrate alternative examples of the surgical drill guide ofthis disclosure; and

FIG. 7 illustrates a surgical drill guide system of this disclosure,including a drill guide and a flexible drill.

DETAILED DESCRIPTION

In the description that follows, like components have been given thesame reference numerals, regardless of whether they are shown indifferent examples. To illustrate example(s) in a clear and concisemanner, the drawings may not necessarily be to scale and certainfeatures may be shown in somewhat schematic form. Features that aredescribed and/or illustrated with respect to one example may be used inthe same way or in a similar way in one or more other examples and/or incombination with or instead of the features of the other examples.

As used in the specification and claims, for the purposes of describingand defining the invention, the terms “about” and “substantially” areused to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. The terms “about” and “substantially” are also usedherein to represent the degree by which a quantitative representationmay vary from a stated reference without resulting in a change in thebasic function of the subject matter at issue. “Comprise,” “include,”and/or plural forms of each are open ended and include the listed partsand can include additional parts that are not listed. “And/or” isopen-ended and includes one or more of the listed parts and combinationsof the listed parts.

Turning now to FIG. 1, an exemplary prior art surgical drill guide 10 isshown. The drill guide 10 generally includes a handle 11 and a shaft 12coupled to the handle 11. In the example shown in FIG. 1, the handle 11is a cannulated handle 11 having a distal portion 11 a, a proximalportion 11 b, and an outer surface 11 c. However, other configurationsof handles 11 are contemplated by this disclosure. For the purposes ofthis disclosure, the handle 11 is manufactured from polymer material viaa molding or machining process. However, other materials and fabricationprocesses known in the art are also within the scope of this disclosure.

The shaft 12 includes a proximal portion 12 a and distal portion 12 b.The proximal portion 12 a of the shaft 12 is coupled to the distal end11 a of the handle 11, for example, via a press-fit. In examples, notshown, the distal portion 12 b of the shaft is straight, extending alongthe longitudinal axis L of the proximal portion 12 a. In the example ofFIG. 1, however, the distal portion 12 b of the shaft is angled relativeto a longitudinal axis L of the proximal portion 12 a, which allows thesurgeon to achieve the ideal insertion angle of a passing drill at aquicker rate, thereby reducing the potential of damage to cartilage andother tissue within the repair site. For the purposes of thisdisclosure, the shaft 12 is manufactured from metal material, such asstainless steel. However, other materials known in the art are alsowithin the scope of this disclosure.

Turning now to FIGS. 2 and 3, the distal portion 12 b of the drill guide10 also includes at least one transverse hole 12 b′. Two holes 12 b′ areshown in FIGS. 2 and 3, however more or fewer than two holes arecontemplated by this disclosure. The holes 12 b′ can be used duringsurgery to view the anchor, specifically the orientation of the anchor,prior to inserting the anchor into bone. The holes 12 b′ may also beused to vent bone and other debris that may become located within thedistal portion 12 b of the guide 12 during surgery. In examples, a theshaft 12 may include a plurality of teeth 14 extending from the distalend 12 c for facilitating maintenance of the guide 10 on the bone duringsurgery, thereby substantially reducing slippage of the drill guide 10off of the bone. In other examples, the distal end 12 c of the shaft 12may have other features known in the art that would help in maintainingthe drill guide 10 on the bone and reduce slippage. For the purposes ofthis disclosure, the holes 12 b′ and the teeth 14 are machined onto theshaft 12. However, other fabrication processes known in the art arecontemplated by this disclosure.

Turning now to FIG. 4A, an example of the surgical drill guide 20 ofthis disclosure is shown. Drill guide 20 is substantially similar todrill guide 10 except as described below. In drill guide 20, the distalend 22 c is narrowed down via a tapered portion 28 relative to theremainder of the shaft 22. In examples, the tapered portion 28 can beformed in one piece (e.g., a swaging operation) or in multiple piecesthat are created separately and assembled together. It is alsocontemplated by this disclosure that more than two distinct diametersets could be included in the distal portion 22 b. In examples (FIG.4E), the tapered portion 28 may also comprise one or more transverseholes 22 b′. The tapered portion 24 also allows for the distal end 22 cto have a smaller diameter than a diameter of the shaft 22. This isadvantageous in surgical procedures which require anchors to be placedas close to an anatomic margin as possible. The smaller distal end 22 callows the center point of the outer diameter to be closer to theanatomical margin, as demonstrated in FIG. 4B, and thus provide a moreanatomical repair. Additionally, the smaller distal end 22 c allows forless of a gap between the outer diameter of the passing instrument andthe inner diameter of the distal end 22 c, resulting in a more accuratetrajectory. For example, if the distal end 22 c had a larger innerdiameter, the angle at which the passing instrument exits the distal end22 c may be larger because the passing instrument would tend to take thepath of least resistance. Notably, the tapered portion 28 could also beincluded in straight guide shafts (not shown).

FIG. 4C is a detailed view of the distal portion 22 b, including theopening 26, the holes 22 b′ and the plurality of teeth 24. FIG. 4D is across-sectional view of the distal portion 22 b of FIG. 4C. As seen inFIG. 4D, the shaft 22 includes a wall 30 defining a bore 32 extendingthrough the shaft 22. The wall 30 furthermore defines the plurality ofteeth 24 extending from the distal end of the shaft 22. Notably, theselection of the diameter D1 of the bore 32 is important for achievingcompatibility with passing instruments. For example, a larger diameterD1 is desirable in the shaft 22, as this allows for more room for anyrigid or semi-rigid portions of the passing instruments to navigate thebend area of the shaft 22. Examples of rigid portions may include arigid drill tip attached to a flexible drill shaft, or a rigid anchorattached to a flexible inserter. However, a smaller diameter D2 of thebore 32 is conversely desirable in the distal end 22 c to tightlyconstrain the exit trajectory of the passing instruments, which resultsin predictable placement of the instruments in bone. However, it is alsoimportant that having a smaller distal end 22 c does not sacrificethickness of the wall 30 and thus the rigidity of the plurality of teeth24. Accordingly, as shown in FIG. 4D, a thickness of the wall 30 isadvantageously maintained or, as shown in FIG. 4E, increased across thetapered portion 28 from the distal portion 22 b of the shaft 22 to thedistal end 22 c. Thus, the shaft 22 and the distal end 22 c of the shaft22 have two distinct inner and outer diameters such that the rigidity ofboth the shaft 22 and the teeth 24 can be maintained.

As stated above, a larger diameter of the bore in the curved region ofthe guide allows for a smaller bend radius and a larger bend angle ofthe drill guide. This configuration is favorable for hard-to-reach orhard-to-visualize anatomical areas. However, as shown in FIG. 4F, wheninserted through the guide 20, passing instruments 34 tend to take thepath of least resistance and cut the corner for the bent distal portion22 b of the guide 20. This results in the passing instruments 34 exitingthe guide 20 at a trajectory having an angle A1 which isnon-perpendicular to the distal end 22 c of the guide 20 andnon-parallel to the central axis C of the bore 32. As described above, asmaller diameter D2 in the distal end 22 c is one method for improvingthe trajectory of passing instruments exiting the guide 20. For example,the larger the diameter D2 in the distal end 22 c, the more misalignedthe exit trajectory angle A1 will be. A reduced distal diameter D2 moreclosely matches the instrument trajectory to the trajectory of the guide20. Notably, another benefit to a smaller distal diameter D2 is that itallows for minimal movement of the passing instruments as they exit theguide 20. Specifically, there is no opportunity for large variationsbetween the trajectory of different passing instruments, such as a drilland an inserter, which could result in additional forces on the passinginstruments or on an anchor during insertion due to a difference in thebone tunnel to inserter trajectory.

FIG. 5 illustrates an alternative example of the drill guide 40 of thisdisclosure. Drill guide 40 is substantially similar to drill guides 10,20 except as described below. As shown in FIG. 5, the drill guide 40includes a proximal outer diameter D4 that is selected to be larger thana distal outer diameter D3. The distal end 42 c of the drill guide 40includes a plurality of teeth 44 for secure placement of the drill guide40 on bone. The teeth 44 are of differing lengths such that they areangled with respect to the distal end 42 c. That is, a projected plane Pacross the distal points of the teeth 44 is angled with respect to theouter diameter D3 of the distal end 42 c such that any misalignmentbetween the passing instruments 34 and the projected plane P of theangled teeth 44 is reduced. Thus, the passing instruments 34 exit theguide 40 at a trajectory having a reduced misalignment angle A2.Notably, this disclosure utilizes only a method of measuring trajectorywith respect to a projected plane P of the angled teeth 44, and not withrespect to the outer diameter D3. It is also contemplated by thisdisclosure that the angled teeth 44 could also be used with guideswithout a tapered portion 48, such as the drill guide 10 of FIG. 1.Additionally, any other drill guide system where an output trajectory ofpassing instruments is important may benefit from the angled teeth 44 ofthis disclosure. In other examples, not shown, the distal outer diameterD3 could be angled with respect to the distal inner diameter D2. Thiswould create the same effect of allowing the passing instruments tobecome more aligned with the predicted trajectory of the guide 40.

As discussed above, a larger inner diameter in the curved region of theguide allows for a smaller bend radius and a larger bend angle, which isfavorable for hard-to-reach or hard-to-visualize anatomical areas.However, a drill guide with a larger and more distal bend angle becomesdifficult to fit through a cannula, which provides a clear access paththrough soft tissue into the repair site. This may result in some curvedguide systems being incompatible with certain sized cannulas.

FIG. 6A illustrates an alternative example of the drill guide 60 of thisdisclosure. Drill guide 60 is substantially similar to drill guides 10,20 except as described below. In drill guide 60, material from the shaft62 of the drill guide 60 is removed at the highest point on the bend,such that the wall 70 defines a flat section 72 in the shaft 62,allowing the drill guide 60 to fit within a narrower cannula 50 than ifthe material had not been removed. The flat section 72 thus allows for atighter bend radius and a more obtuse angle of the drill guide 60without sacrificing rigidity of the shaft 62 or the teeth 64.Additionally, in examples, a top tooth 64 of the drill guide 60 ismodified or removed, further facilitating the passage of the drill guide60 through the cannula 50, as compared with a drill guide 60 having atop tooth 64 that has not been modified or removed, as shown in FIG. 6B.

As stated above, the drill guides described herein may be used forpassing an instrument, such as a drill, into a repair site. A curveddrill guide necessitates the use of a flexible drill to pass around thebent region of the guide. Currently, some flexible drills are made ofsuperelastic Nitinol. Another material state of Nitinol, calledmartensitic Nitinol, is desirable in that it takes a permanent set whenbent, which means that the forces required to push the drill around thebend are even lower than those required for superelastic Nitinol.Superelastic Nitinol is able to deform up to 8% strain and return to itsoriginal shape without permanent deformation. Martensitic Nitinol isable to reach similar strains, however it requires even less force todeform/bend than superelastic Nitinol. The low forces required to deformmartensitic Nitinol make it an ideal state of Nitinol for curved guidenavigation.

Examples of flexible drills of this disclosure utilize the materialproperties of Nitinol to control the amount of force it takes pass theNitinol around the bend of the curved drill guide. Specifically, Nitinolcan be composed of metallic states called Austenite, Martensite, andR-Phase. The metallic state of Nitinol is dependent upon certainmaterial properties called transition temperatures. The transitiontemperatures available for Nitinol are austenitic start (As), austeniticfinish (Af), martensitic start (Ms), martensitic finish (Mf), R-phasestart (Rs), and R-phase finish (Rf). For a martensitic state of Nitinol,the operating temperature of the drill should be below the Astemperature. Therefore, an As temperature above the operatingtemperature would ensure a more martensitic (i.e., shape memory) stateof Nitinol in the drill. In a curved medical drill application, forexample, the As temperature could be specified to be above both thetemperature of the operating room and the body temperature of thepatient. For different guide bend geometries and environmentaltemperatures, different transition temperatures could be specified.

One problem with martensitic Nitinol is that it is extremely flexible,which makes machining difficult. Superelastic Nitinol is more easilymachined than martensitic Nitinol, since it is more rigid. Therefore,the geometry of the flexible drill can be more easily machined onNitinol while the Nitinol is in the superelastic state. As stated above,Nitinol is capable of being heat treated to modify the transitiontemperatures (Af, As, Mf, Ms, Rs, Rf) to make the final productmartensitic with respect to certain environmental temperatures.Therefore, one method of obtaining a martensitic drill in the finalstate is to machine the Nitinol in its superelastic state by setting theinitial Af temperature below the operating temperature of themanufacturing environment. The drill can then be heat treated to make itmartensitic after machining. Another method would be to procure theNitinol in a martensitic state and then heat it up during machining (forexample, through hot air, fluid, or changing the environmentaltemperature of the machining) to a temperature above the Af temperatureso the Nitinol is in a superelastic state. After machining, the Nitinolof the drill would cool down back to its martensitic state for use, andtherefore no heat treatment would be required, eliminating amanufacturing step.

An additional problem with Nitinol drills is that, when the drill ispowered on, a martensitic Nitinol wire tends to whip around in circlesat the speed of the drill, which poses a safety hazard to the user andpatient. Martensitic Nitinol can also be so soft that the user losestactile feedback from the drill during the drilling process and/or theuser cannot manually maintain axial alignment of the drill within thedrill guide. Accordingly, it would be advantageous to have a means ofminimizing the amount of whip that occurs with martensitic Nitinol, aswell as providing additional stiffness to the drill.

FIG. 7 illustrates an exemplary drill guide system 100 of thisdisclosure. Drill guide system 100 generally comprises a drill guide 80and a drill 90. Drill guide 80 is substantially similar to drill guides10, 20 except as described below. The drill 90 is comprised ofmartensitic Nitinol and includes a stiffening sheath 92 disposed overthe part of the drill 90 that does not need to navigate the bend of thedrill guide 80. Since the sheath 92 does not extend into the curvedregion of the drill guide 80, it does not need to be made of a bendablematerial, so long as the material of the sheath 92 is selected to bemore rigid than the material of the drill 90. The remaining length ofthe drill 90 can be left unsupported. The sheath 92 advantageouslyminimizes the amount of whip that occurs if a user were to power thedrill 90 in free air. Additionally, the sheath 92 allows compressiveforces to be applied during use without the risk of buckling of thedrill 90, and provides the necessary stiffness to effectively transmitthose forces to the tip 94 of the drill 90. Finally, the sheath 92allows for a tighter fit of the drill 90 to the bore 84 of the drillguide 80, allowing for the drill 90 to maintain radial alignment to theguide 80. It is further contemplated by this disclosure that the sheath92 may be used for drills of any materials and/or geometries thatrequire increased stiffness over some fraction of their length, forexample, small diameter stainless steel wires, and for drill guideshaving straight guide shafts.

Another method of minimizing the amount of whip would be to change thetransition temperature as described above of only the section of drillthat needs to be flexible. For example, the most distal two inches ofNitinol could be in a martensitic state, whereas the rest of the drillcould be superelastic. Examples of methods of making only a portion ofthe drill martensitic are using specialized heat treat ovens, heattreating through partial immersion in a liquid, or using heating coilscapable of applying concentrated heat to a localized area.

While this disclosure has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of the presentapplication as defined by the appended claims. Such variations areintended to be covered by the scope of this present application. Assuch, the foregoing description of examples of the present applicationis not intended to be limiting, the full scope rather being conveyed bythe appended claims.

What is claimed is:
 1. A method of surgical drilling comprising:introducing a surgical drill guide to a repair site, the surgical drillguide comprising: a shaft having a proximal portion and a distalportion, the distal portion including a tapered portion and a distalend, an outer diameter of the proximal portion selected to be largerthan an outer diameter of the distal end, the proximal portion and thedistal end separated by the tapered portion; and a bore defined by awall of the shaft extending from a proximal end to the distal end of theshaft, the wall defining a plurality of teeth extending from the distalend; wherein a thickness of the wall of the distal end is selected to bethe same as or greater than a thickness of the wall of the proximalportion; and passing a flexible drill through the bore from the proximalend to the distal end of the shaft; wherein the flexible drill furthercomprises a sheath extending through the bore from the proximal end to aregion proximal to the distal portion of the shaft.
 2. The method ofclaim 1, wherein the flexible drill comprises Nitinol.
 3. The method ofclaim 2, wherein the Nitinol is capable of deforming up to 8% strain andreturning to an original shape without permanent deformation.
 4. Themethod of claim 1, wherein the sheath comprises a material selected tobe more rigid than a material of the flexible drill.
 5. The method ofclaim 1, wherein the distal portion of the shaft is angled relative to alongitudinal axis of the proximal portion of the shaft.
 6. The method ofclaim 1, wherein the distal portion of the shaft includes at least onetransverse hole in communication with the bore.
 7. The method of claim1, wherein the tapered portion is formed in one piece.
 8. The method ofclaim 1, wherein the tapered portion is formed in multiple pieces.